Effects of wet distillers bran plus solubles and corn oil in diets containing flint corn grain and citrus pulp for finishing Nellore bulls

Objectives were to evaluate the effects of de-oiled wet distillers bran plus solubles (WDBS) as a protein source [when included at 150 g/kg of diet dry matter (DM)] to replace soybean meal (SBM); or as a protein and energy source (when included at 300 and 450 g/kg of diet DM) to replace a mix of soybean meal, ground flint corn, and citrus pulp, and to evaluate the effects of corn oil inclusion (0vs 30 g/kg of diet DM) in diets containing 0 to 450 g/kg of WDBS (DM basis). Two hundred and thirty-two Nellore bulls (BW = 425 ± 25 kg) were used in a randomized complete block design with a 2 × 4 factorial arrangement of treatments consisting of diets supplemented or not with 30 g/kg of corn oil (DM basis) each one combined with 4 inclusions of WDBS (0, 150, 300, and 450 g/kg; DM basis). Bulls were blocked by initial shrunk BW and allocated into 40 pens (5 pens/treatment; 5 or 6 bulls/pen). Effects of corn oil × WDBS interaction were not detected (P ≥ 0.29) for feedlot growth performance, carcass traits, and dietary NE concentrations, except for dry matter intake (DMI; P = 0.03). Increasing inclusion of WDBS linearly decreased DMI (P = 0.004) of finishing bulls fed diets without corn oil supplementation, but quadratically decreased DMI (P = 0.002) in diets containing 30 g/kg of corn oil, resulting in the observed interaction (P = 0.03). Feeding WDBS did not affect average daily gain (ADG), hot carcass weight (HCW), and dressing percentage of finishing bulls regardless of corn oil supplementation (P ≥ 0.18). Feed efficiency (G:F) tended (linear; P = 0.09) to increase due to WDBS inclusion. The inclusion of 30 g/kg corn oil (DM basis) in the diet tended (P = 0.07) to decrease DMI by 3% and increase G:F by 7.5% compared with diets not supplemented with corn oil. Including 30 g/kg of corn oil (DM basis) in the diet increased (P = 0.05) observed net energy of maintenance (NEₘ) and net energy of gain (NEg). Corn oil supplementation had no effect (P ≥ 0.19) on final BW, ADG, HCW, and dressing percentage. In summary, WDBS is as a protein supplement alternative to SBM when fed at 150 g/kg of the diet DM. The supplementation with corn oil is an effective way to increase the energy density of finishing diets containing WDBS.